diff --git a/util-internal.h b/util-internal.h
index f52ae3f4..9251758e 100644
--- a/util-internal.h
+++ b/util-internal.h
@@ -102,6 +102,10 @@ extern "C" {
 	((e) == ECONNREFUSED)
 
 #else
+/* Win32 */
+
+#define EVUTIL_ERR_IS_EAGAIN(e) \
+	((e) == WSAEWOULDBLOCK || (e) == EAGAIN)
 
 #define EVUTIL_ERR_RW_RETRIABLE(e)					\
 	((e) == WSAEWOULDBLOCK ||					\